Jimmy Golen, a sports writer for The Associated Press in Boston who was in Southern California for the holidays, said he and other tourists saw the long, glowing contrail while touring Warner Bros. studio in the Los Angeles suburb of Burbank.

"People were wondering if it had something to do with movies, or TV or a UFO," he said. "It was very cool."

The same rocket carried Iridium satellites into orbit in June. That time, the first stage landed on a floating platform in the Pacific Ocean. This time, the rocket was allowed to plunge into the sea.

It was the 18th and final launch of 2017 for SpaceX, which has contracted to replace Iridium's system with 75 updated satellites. SpaceX has made four launches and expects to make several more to complete the job by mid-2018.

The satellites also carry payloads for global real-time aircraft tracking and a ship-tracking service.